Spark plug shielding



Junelfi, 1942. J. J. MAscucH SPARK PLUG SHIELDIHG Filed Sept. 13, 1930 MW a u 0.

INVENTOR.

H B. U E. m i H m. E. JY B AT RNEY.

Patented June 16, 1942 UNITED I STATES PATENT oFFrcE SPARK k Applicatlzi481,788

18 Claims.

This invention relates to spark plug shielding and has for an object toprotect spark plugs as used on internal combustion engines and to shieldsuch plugs against electronic emissions thereby preventing interferencewith radio apparatus. Other objects or the invention will be understoodfrom the following specification and the accompanying drawing, selectedto show my invention in several forms, and in which, Fig. 1 is asectional elevation of an engine cylinder with a spark plug andconnection shielded according to this invention, Fig. 2 is a modifiedconstruction alternative to Fig. l with the engine cylinder sectioned,Fig. 3 is a form of sheet metal shield for the spark plug, partlysectioned to show the interior construction.

The use of radio apparatus in the vicinity of internal combustionengines requires the spark plug connections to be enclosed with ametallic casing which is grounded to prevent interference with the radioset. It has also been found that spark plugs as used on airplane engineswhen in high altitudes lose some of their insulating qualitiesv due tothe rarifled air in which they are operating, which condition isremedied in the present invention by placing the spark plug in a hollowvessel filled with transformer oil and provided with a. suitable cap toretain the contents. This hollow vessel may be screwed into the enginehead and provided with exterior fins for cooling the contents.

Air cooled aviation engines in particular are subject to local hot spotsin the combustion chambers which limit the usable compression ratio andtherefore the power output. For example, there is usually a hightemperature zone at the spark plugs and adjacent combustion chamberwall, particularly in the case of plugs located on the leeward side ofan air cooled cylinder head.

The present invention provides additional radiating means for suchpoints without change in the present standardized dimensions of theplugs, which should remain interchangeable between various enginedesigns.

According to the present invention, an extenslon in intimate thermalunion with the cylinder head is disposed about the spark plu to form abase for the application of a substantially increased number and area ofcooling fins.

In the preferred form shown in the drawing the extension is indicated asbeing conveniently formed integral with the usual spark plug holebushing and comprises an enlarged cylindrical extension surrounding theplug and provided with a plurality of integral annular radiating fins.

This cooling element is preferably made of material of high thermalconductivity, 1. e., a material characterized by a relatively smalltemperature gradient, whence it will be seen that the bushing into whichthe spark plug is screwed will be substantially reduced in temperature,with a corresponding reduction in the temperature of the spark plugitself and of the surrounding cylinder wall.

The stem of the spark plug is connected through an elbow with theconductor in a novel manner which admits of quick replacement andinsures complete metallic shielding.

Referring to the drawing, II is a. sectioned view of the engine cylinderhead which is provided with cooling fins I 2 and a sleeve IS. The sparkplug, which is of the usual commercial type, is indicated at H and theconductor from the spark plug is indicated at IS.

The shield in Fig. 1 comprises the hollow con- I tainer l6 which isscrewed into the engine head at H and is provided with the cooling finsIS. The threaded base of the spark plug l 4 is screwed into thecontainer it at l9. In this construction the spark plug is removed withthe container.

The container I6 is provided with a cover 2| of insulating materialwhich is covered on the outside with a metallic shield 22, which ispreterably applied by electro-plating. This cover is made in the form ofan elbow with a collar at 23 which seats on the rim of the container isend encloses the interior. The interior of the cover is formed in ahollow cone as indicated at 24 and is provided with a metallic washer at25 centered over the stem of the spark plug and threaded to receive thescrew 26. The cover 2| is held on the container l6 by means of a bail 54carried by the container I6. e

The screw 26 clamps the coil spring 21 in place to engage the stem ofthe plug and is adjustable for stems of diflerent lengths. Screw 26 isprovided with a tapered point as shown which penetrates the insulatingwall of the conductor l5 and engages the stranded conductor 28,effectively making connection therewith. A washer is provided at 29 onthe end of conductor ii to which the strands of 28 are soldered with theobject of .holding the strands and insulation in place. The shank of theelbow 30 is provided with a threaded ferrule to receive the clamping nut3| which clamps the tapered rubber washer 32 to make a waterproofedconnection at the outlet. The conductor I5 is provided with a suitablemetallic coating for grounding purposes. The conductor l may also beprovided with a shielding conduit as shown in my co-pending applicationSerial No. 394,618, filed September 23, 1929.

In Fig. 2 the container for the spark plug is made of a short piece oftubing seated On the engine head and suitably secured in position. Thetubing ll seats in a turned groove at 43 in the casting of the head I Iand is held in place by the set screws 42 in the air cooling fins of theengine. This construction is less expensive than that shown in Fig. 1and may be adapted to existing engine heads. The cover 2| is held inposition by the bail 54.

In Fig. 3 a hollow container is preferably spun 7. A spark plug shieldcomprising a cup to surround the spark plug and a cap for the cup, saidcup and cap being liquid-proof and said cup being adapted to be filledwith a. dielectric liquid to increase the insulation of the plug.

8. A spark plug shield comprising a metallic cup to surround the plugand a'cap of dielectric material for the cup .providedwith a-collaradapted seat on said cup, ametallic cover on said cap in the form of a'thin sheath which is grounded to. said cup, and a sleeve of dielectricmaterial betw" en said cup and the spark plug to prevent flashes fromthe spark plug to said cup.

from sheet stock and is held in place by the flange of the spark plug.The container 5i has a base flange at 52 which is clamped against theengine casting by the flange .of.- the spark plug. The rim is curledover at 53 to provide a seat for thecover 2| and to support the bailwhich holds the cover in place by spring action.

It is apparent that the hollow chamber surrounding the spark plu inFigs. 1, 2 and 3 can be filled with a suitable di-electric in liquid orplastic form to increase the insulation of the spark plug. It will benoted that the extension of the cover atv 24 into the container andbelow the metallic coating 22 increases thesparking distance between thestem of the spark plug and its metallic enclosure.

The invention may be applied in other forms additional to those shown.

Having thus described my invention, 1 claim:

1. A shield for a spark plug comprising a sleeve enclosing the sparkplug, a cover for said sleeve comprisin a body of insulation coated withmetallic foil, a collar on said cover resting on said sleeve and makingelectrical contact with said coating and means for securing said coverto said.

sleeve.

2. A shield for a spark plug comprising a. sleeve enclosing the sparkplug, a cover for said sleeve comprising a body of insulation coatedwith metallic foil, a collar on said cover resting on said sleeve andmaking electrical contact with said coating, a. conductor outlet in saidcover and means for securing said cover to said sleeve.

3. A shield for a spark plug comprising a sleeve enclosing the sparkplug, a cover for said sleeve comprising a body of insulation coatedwith metallic foil, a collar on said cover resting on said sleeve andmaking electrical contact with said coating and means for securing saidcover to said sleeve to make a moisture-proof closure.

. 4. A shield for a spark plug comprising a sleeve enclosing the sparkplug, a cover for said sleeve comprising a body of insulation coatedwith metallic foil, a collar on said cover resting on said sleeve andmaking electrical contact with said coating, a conductor outlet in saidcover and.

means for securing said cover to said sleeve so that the conductoroutlet may extend in various directions from said sleeve.

5. A spark plug shield comprising a cup to surround the spark plug and acap for the cup, said cup being adapted to be filled with a semisoliddielectric substance to increase the insula tion of the plug. I

6. A spark plug shield comprising a cup to surround the spark plug and acap for the cup', said cup and cap being moisture-proof and said cupbeing adapted to be filled with a semi-solid dielectric substance toincrease the insulation of the plug.

I 9. The combination with an engine cylinder, a spark plug and a radioshielded cable therefor; of a shielding shell secured to the cylinderand surrounding the spark plug and having an opening therein at itsouter end for the insertion and removal of the spark plug, a capcovering said outer end opening and comprising a conductor, a metallicsheath, and an insulating lining extending between theterminal'end ofthe spark plug and the wall .of the shielding shell, and means to engageeach component part of the cap with the corresponding component parts ofw shape admitting of its fitting engagement within the space between theterminal end of the spark plug and the inner wall of said shell, ametallic shielding within which the normally exposed portion of said capis encased, a conductor means in said cap contacting with theterminaliend oi the spark plug, and means to engage each com- I.

ponent part of said cap with the corresponding component parts of theradio shielded cable.

11. The combination with an engine cylinder, a spark plug and a radioshielded cable therefor; of a shielding shell encircling the spark plugand bearing at its inner end on the engine cylinder and open at itsouter end to admit of the insertion and removal of the spark pliIg,a capcovering said outer end opening-and comprising a conductor, a metallicsheath, and an-insulating lining within the embrace of which theterminal end of the spark plug is seated, and means to engage eachcomponent part of the cap with the corresponding component parts of theradio shielded cable.

12. The combination with an engine cylinder, a spark plug, and a radioshielded cable therefor; of a shielding means comprising a base memberbearing on the engine cylinder, a cap detachably seated on said base tocomplete the enclosure of the spark plug and comprising a conductor, ametallic sheet, and an insulating lining into which the spark plugextends, and means to engage each component part of the cap with thecorresponding component parts of the radio shielded cable.

13. A device for cooling the hot spot in the wall of an engine cylinderin the vicinity of the spark plug and the spark plug itself comprisingan exteriorly finned metallic shell surrounding substantially the entireprojecting length of the spark plug, the wall of said shell being whollyindependent of and spaced from the structure of the spark plug wherebythe latter may be bodily removed and withdrawn without disturbing in anyway the connection between said shell and the engine cylinder.

14. A device for cooling the hot spot in the wall of an engine cylinderin the vicinity of the spark plug and the spark plug itself comprisingan exteriorly finned metallic shell having an exteriorly threadedbushing and a shoulder around said bushing, both said shell and saidbushing being in intimate'thermal contact with the cylinder wall; thefinned portion of said shell being substantially coextensivewith theentire projecting length of the spark plug and being open at its outerend to admit of the spark plug being bodily removed and withdrawn fromsaid shell without disturbing in any way the intimate thermal contactaforesaid, and said shell having formed therein at its inner end andwithin said bushing a threaded opening into which the inner end of thespark plug is screwed.

15. In a radio shield for spark plugs, a cap to cover a plug, said capcomprising a metal shell and a body of dielectric material in the shell,a lateral extension on said shell and dielectric body provided with abore to receiv a conductor, a washer carried by the dielectric body, anda contact means disposed through said washer, the lower end of saidcontact means'being adapted to contact a spark plug and the upper endthereof being adapted to project into said bore to contact a conductor.

16. In a radio shield for spark plugs, a cap to cover a plug, said capcomprising a metal shell and a body of dielectric material in the shell,a lateral extension on said shell and dielectric body provided with abore to receive a conductor, a threaded bushing carried by saiddielectric body, a contact screw adapted to be inserted into the borethrough the bushing for the purpose of piercing the insulation of andmaking contact with a conductor in the bore and a resilient contactmeans carried by the screw to make contact with a spark plug.

17. In a radio shield for spark plugs, a cap to cover a plug, said capcomprising a metal shell and a body of dielectric material intimatelyattached to said shell, said shell and body each having a. lateralextension formed with a bore to receive a conductor and a partiallyresilient contact means removably supported from said dielectric body,the upper end of said contact means being adapted to pierce theinsulation-oi and make contact with a conductor in the bore and thelower end of said contact means adapted to extend below the dielectricbody to make contact with a spark plug.

18. In combination with a spark plug and a cable therefor, a spark plugshield comprising a bushing disposed in the cylinder head around thespark plug and formed with an extension projecting above the surface ofthe cylinder head and surrounding the base of the spark plug and a capdisposed over the upper part of the plug and in electrical contact withthe extension on the bushing.

JOSEPH J. MASCUCH.

